When two surfaces are brought in contact with each other, a transfer of electrons may occur resulting in a residual static electrical charge when the surfaces are separated. This phenomena is known as triboelectricity or generally as static electricity. As surfaces move in contact past each other, significant electrostatic charges can be built up on the surfaces, thereby creating strong electric fields.
One of the problems associated with sensitive electronic components is that the fields or discharge of even a relatively small electrostatic charge in close proximity to the component can damage the component. For example, an electrostatic charge on a surface of the electronic component or on the surface of a user can be discharged when that user comes into contact with the device. Such a discharge can destroy the sensitive circuitry internal to the device.
To provide protection from electrostatic discharge, it is well known in the art to place sensitive electronic components into anti-static packaging that employs the Faraday cage effect. The Faraday cage effect relies on the fact that electricity generally does not penetrate a conductive enclosure, but rather the electrical discharge will go around the enclosed space, perhaps on the surface of the enclosure, seeking the path of least electrical resistance en route to the lower potential it is pursuing.
A Faraday cage is recognized in the art as a substantially enclosed, at least partially conductive, structure. By substantially surrounding a static sensitive device with an electrically conductive or electrostaticly dissipative enclosure, the device is shielded from damaging electrostatic charges originating outside of the enclosure. Electrostatic dissipative materials have been generally defined as having a surface resistivity of between 10.sup.5 and 10.sup.12 ohms/square.
However, such anti-static packaging must respond to other variables in the environment in which it is actually used. For example, the electronic component is typically inserted inside the packaging and later removed from the packaging for use. Both insertion and removal of the electronic component provide an opportunity for a electrostatic discharge, especially if a human operator is involved. Thus it is important to reduce the risk of damage by electrostatic charges when the component is inserted into an anti-static package and again when that user or another user removes the electronic component from the anti-static package. By keeping the component away from direct contact with any user inserting or removing the device from the anti-static package, the opportunity for a destructive electrical discharge via the user is reduced. A variety of methods have been employed to reduce the risk of damage by electrostatic charges when a user is manipulating an electronic component, but these typically require the user to use other devices or tools other than the package itself to manipulate the object. It would be advantageous to provide a mechanism to allow the user manipulating the electrical component to use the anti-static package itself to reduce the risk of damage by electrostatic charges. It would alto be desirable to do so without creating any significant additional electrostatic charges. Furthermore, the package should be easier to manipulate than existing packages with anti-static features.
Another problem encountered in packaging electronic components is that many such components include leads extending beyond the surface of the component. Particularly in surface-mount technology, chip leads are often so small and closely spaced together that even a relatively minor contact between the leads and other objects can deform the chip leads, necessitating difficult repair efforts or scrapping of an otherwise operational device. It would be advantageous to provide an anti-static package wherein the possibility of deforming such leads is minimized during shipping and handling.
Another difficulty to be overcome is that such an anti-static package should be able to accept electronic devices of a range of sizes and not just one specific size. Such a feature would simplify the process of packaging electronic components by decreasing the number of different anti-static packages required to accommodate a variety of products in the allowed size range. At the same time the anti-static package must itself be readily capable of being packaged, in some instances, for further anti-static protection.